I'm not sure which fan I'm getting yet, it's only a socket A CPU so it shouldn't take too much to cool it down. There's a nice coolermaster fan in a local store that looks nice. Got pretty lights and everything! lol

It may just be that the thermal pad has worn away and needs replacing, but I may as well put a bigger fan on there to make sure. It's been idleing at 50c - 55c and can go up to 66c under load on a hot day so something needs to be done. I've already taken the side casing off and the temperature increases by about 5c when I put the side back on. I've got two 80mm fans blowing the air out of the back.

Thanks for your quick reply. I'll just use a cloth and maybe a cotton bud?

There's no more spaces for fans on the case. The side is mainly plexiglass, the front is taken up with the optical drives and power buttons and there is just the two spaces at the back for the fans. I guess it's an old case. I'm hoping that it's just the thermal pad that's causing the problem and when I replace it the temps come down. If not I'll look at getting a new case with better ventilation. Many thanks for your help.